1. Field of the Invention
The present invention relates to the data processing field, and more specifically to a load balancing method and a corresponding system.
2. Description of the Related Art
Load balancing methods are commonly used in data processing systems with a distributed architecture, wherein several clients rely on resources managed by multiple servers. The object of the load balancing methods is that of distributing the requests coming from the clients across the servers, such that overall performance of the system is increased.
A typical example is that of a server farm, which consists of a cluster of mirrored servers; the mirrored servers store identical information and provide the same services to the clients. The clients access the server farm through a router, which is the only unit visible to the outside. Whenever a client attempts to contact the server farm, the corresponding request is received by the router, which selects the server in the cluster that is best suited to handle the request.
For this purpose, a number of different algorithms have been proposed in the last years. A conventional approach consists of assigning each request to the servers according to a round-robin policy. More sophisticated techniques propose detecting a workload of each server; the server having the lowest workload is then selected for servicing the request.
An additional problem arises when information specific for each client must be stored on the servers (such as in a licensing management application). In this case, when the number of clients is very high (for example, more than 100,000), it is not feasible to replicate the specific information for all the clients on the different servers. A solution commonly adopted is that of dynamically assigning each client to a preferred server, which only stores the specific information for the corresponding clients; all the requests of each client are then transmitted to the preferred server directly. Whenever the client switches to a different server, the corresponding specific information is transferred to the new preferred server.
However, in these environments the load balancing methods known in the art are not completely satisfactory. Indeed, the techniques commonly used involve frequent switching of the clients between different preferred servers. As a consequence, the specific information of the clients must be continuously moved across the system. These operations adversely affect the overall performance of the system, and can defeat the advantages provided by the load balancing method.